Fault Systems And Reservoir-controlling Mechanisms In The North Of Chaidamu Basin

By use of geological dates such as seismic dates and logs, on the basis of studying the faulting geometrical feature at the north of Caidamu basin , combined tectonic evolution sections, the fault kinematics features analyzed systematically, fault formation and active stages made clear, fault systems divided, fault types on the north of Caidamu basin, the faults can be divided into 3 types: (1) basement involution fault that throw to the earth surface, (2) basement involution fault that throw to de up member of Xiaganchaigou formation and Shangganchaigou formation, (3) overlying formation slip fault that throw to the earth surface from two detachment zones, up member of Xiaganchaigou formation and Shangganchaigou formation. According to the coupling relationship between fault activity period and reservoir forming period, the role of different types of faults to reservoir forming has been analyzed. It has been pointed out that basement involution faults that throw to the up member of Ganchaigou formation are the oil source faults to lower structure layer. It has also been pointed out that basement involution faults that throw to the earth surface are the oil source faults to lower structure layer on the early stage, while they act as dissipation faults of lower structure to release the hydrocarbon accumulated earlier on the later stage, and the hydrocarbon partly accumulates in the upper structure, partly dissipates. The overlying formation slip faults connect with basement involution faults that throw to de up member of Ganchaigou formation, which adjust the lower structure layer to the upper. Synthesizing the seal mechanism of faults and their effecting factors, fault seal of typical areas in the north of Chaidamu basin has been dissected. The results show that the fault seal in Caidamu basin is mainly clay smear and phyllosilicate-framework fault rock seal.According to the results of petroleum reservoir controlling mechanism, the process of hydrocarbon migration and accumulation has been summarized and the fracture-controlled accumulation model has been divided into 3 types: (1) early accumulation-late preservation type; (2) early accumulation-late adjustment type; (3)late accumulation type. And several favorable areas have been forecasted at the north of Caidamu basin.